Custom message when someone tries and fails to get the entity. Can be either a string or a function(ply, entTable).
See here.

getPrice(required if price field is not given)

Set this field to a function that returns the price. This is handy if you want the price to change under certain conditions (eg. for donators)
This function gets called with two arguments:

The player buying the entity.

The price set in the price field, if any.

Because the price field gets passed into the function, this getPrice field can be used in conjunction with the price field. This is handy if you want to apply a multiplier to the price. Do note that you should always return a value for all possible situations, even if it is just the price argument without modification, as this function will override the price field.
Example:

Set this field to a function that returns the maximum amount of entities a player can buy. This is handy if you want the max to change under certain conditions (eg. for donators).
This function gets called with one argument: the player buying the entity.